A tire includes a pair of beads. A carcass is extended on and between the beads on both sides.
Each bead includes a core and an apex. The apex extends outward from the core in the radial direction. The apex is formed of a highly hard crosslinked rubber, and typically has a length of about 35 mm.
The carcass of the tire is formed by a carcass ply being turned up around the cores. Thus, the carcass ply includes: a main portion that extends from the equator plane toward each core; and turned-up portions each of which extends radially outward from the core along the apex.
In the tire, a bead portion is fitted into a rim. In a running state, the bead portion is under a heavy load. Therefore, durability in the bead portion is important. Various studies are made for the durability in the bead portion. An example of the study is disclosed in JP2005-255047.
As described above, in a running state, the bead portion is under a heavy load. Therefore, stiffness of the bead portion is important.
Various studies are made for arranging the structure of the bead portion and controlling stiffness of this portion. An example of the study is disclosed in JP2012-025280. In the tire disclosed therein, an apex (hereinafter, also referred to as a small apex) having a length less than a conventional apex is used for the bead. Further, another apex (hereinafter, also referred to as a support layer) is disposed axially outward of the turned-up portion of the carcass. In the tire, by the structure of the bead portion being thus arranged, durability is improved and weight is reduced.